1. Field of Invention
The present invention relates to an apparatus and method for controlling a urea injection amount of a vehicle that controls urea injection in consideration of a difference between an internal temperature change rate and a regeneration temperature of an SCR integral diesel particulate filter that is mounted in a diesel vehicle.
2. Description of Related Art
In order to purify NOx, an SCR catalyst receives urea from an injector that is disposed at the front end thereof and acquires ammonia that is generated according to evaporation and decomposition of the injected urea.
In order to provide cost reduction, weight reduction, and efficient package of an aftertreatment device, an SCR integral diesel particulate filter is applied.
The SCR integral diesel particulate filter is an aftertreatment device that coats an existing diesel particulate filter with an NOx purifying function catalyst and removes an SCR carrier and canning, compared with an aftertreatment device in which an SCR catalyst and a diesel particulate filter are separated and thus a weight thereof is reduced, and accordingly a cost can be reduced and fuel consumption can be improved.
In the SCR integral diesel particulate filter, because an SCR catalyst may be moved and mounted at the upstream side of an exhaust pipe, a heat-up function for securing an NOx purifying performance is unnecessary and thus an NOx purification performance can be improved and fuel consumption can be enhanced.
Because the SCR integral diesel particulate filter receives urea at the front end of a diesel particulate filter, it is necessary to control urea injection timing/injection amount in consideration of regeneration temperature control precision by urea injection while regenerating.
When urea is injected while regenerating the SCR integral diesel particulate filter, a regeneration temperature is deteriorated by an increase of a heat capacity of an exhaust gas and thus when increasing a urea injection amount to a predetermined amount or more, in order to secure a target regeneration temperature, a fuel injection amount should be additionally increased and thus fuel consumption is worsened.
Further, at the rear end of the diesel oxidation catalyst, as a slip amount of HC increases, an internal temperature of the SCR integral diesel particulate filter rises, and when abnormal regeneration occurs, a temperature sharply rises and thus degradation of an SCR catalyst may be promoted and the filter may be damaged.
Examples of known devices include Japanese Patent Laid-Open Publication No. 2006-274986 (Oct. 12, 2006) and Japanese Patent Laid-Open Publication No. 2011-052610 (Mar. 17, 2011).
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.